1. Field of the Invention
The invention relates to an optical modulator which modulates the intensity of a light beam in response to a sampled analog electrical signal. The invention further relates to a system which utilizes such a modulator to transmit signals from an array of infrared detectors contained within a cryogenic chamber.
2. Discussion
Sensor systems commonly use a mosaic focal plane array of infrared (IR) detectors contained within a low-temperature, cryogenic chamber. The reason for the use of a cryogenic chamber is that the IR detector can only operate at a specified cryogenic temperature and thus the readout circuit must also operate at the same temperature of the IR detector in order to maintain the desired signal-to-noise ratio.
To deliver the signals outside the chamber, a transmission line in the form of a coaxial cable or twisted shielded wire is used. The distributed capacitance of the transmission line, as well as the capacitance between the transmission line and the cryogenic chamber (which generally has metallic walls), limits the speed of data transmission.
One solution to the capacitance problem is to use an optical transmission line. This optical interface eliminates heat transfer into the cryogenic chamber through conventional wire, eliminates electromagnetic interference including cross talk and noise pickup, eliminates high-power transmission line drivers with transmission loads, and has advantages of weight and sizes.